Various methods and arrangements for coupling light waves propagating from one optical fiber to another optical fiber are known. For example, U.S. Pat. No. 3,666,345 to Maslowski discloses end-to-end coupling of optical fibers using a hologram as an optical transmitting device. These types of end-to-end arrangements, however, take up a relatively large amount of space and may be impractical for applications that require a compact optical fiber coupler. In addition, proper alignment of the fibers in end-to-end devices is critical and is difficult to obtain. If the end-to-end fibers are aligned improperly, the coupler produces unacceptable insertion loss.
Optical fiber couplers for a plurality of parallel optical fibers are disclosed in U.S. Pat. No. 3,883,223 to Hudson and U.S. Pat. No. 4,722,582 to Modone et.al. The couplers disclosed in these patents couple a bundled, parallel arrangement of a plurality of optical fibers positioned relative to a concave reflective surface such as a spherical mirror whereby the optical signal from one fiber is transmitted to at least one of the remaining fibers in the bundle. This arrangement lessens the alignment problem encountered with end-to-end fiber couplings. However, spherical mirror couplers are not sufficiently compact for many commercial applications. In a spherical mirror coupler, the greater the number of parallel fibers employed, the farther away the spherical mirror must be placed in order to maintain the necessary acceptance angle for the optical fibers to minimize attenuation of the optical signal. Thus, the number of fibers that can be utilized in a compact structure is limited.